1. Field of the Invention
This invention relates generally to cinematographic projection systems and in particular to the utilization of such systems in conjunction with vehicle simulators to provide a realistic environmental scene for training purposes.
2. Description of the Prior Art
While the invention is applicable to simulators of any manner of vehicle, it will be described herein for the purposes of example in conjunction with an aircraft flight simulator which is believed at this time to be its principal field of utility and importance.
In aircraft flight simulators and similar training devices, it is often necessary to provide a visual system for presenting to the operator (trainee) a realistic scene representing an environment appropriate to the position, condition, altitude, etc., of the simulated aircraft at any given moment. Various types of visual systems have been developed including one known as a "camera-model," which utilizes closed-circuit television (CCTV) and a two- or three-dimensional terrain model. The TV camera and an optical pickup or "probe" are mounted for displacement in six degrees of freedom and positioned to generate an aerial view of the terrain model. The position and altitude of the camera/probe unit is controlled in response to manipulation of the simulator controls and the resulting scene is displayed to the trainee with a CRT. Thus, in effect, the camera/probe "flies" over the model terrain, representing the eyepoint of the simulator pilot and displays for him the scene which he would view through the windshield if his simulator were a real aircraft flying over real terrain. For additional information on camera-model visual systems reference may be had to U.S. Pat. Nos. 2,979,832 and 3,422,207.
Camera-model visual systems have a number of drawbacks, perhaps the most important one of which is the limited brightness and resolution of the TV display together with the presence of raster lines which detract from its realism. And, of course, the better the resolution, the more realistic the model must be if it is to appear life-like in the display, and the more realistic the model, the higher its cost and the more difficult its maintenance. In addition, a terrain model of suitable scale can be accommodated only in an extraordinarily large room or a specially designed building.
These and other disadvantages of camera-model visual systems are avoided by using motion picture film as the image source. The film is made with a forward-looking cine camera mounted in an aircraft which flies a planned mission over the desired terrain, making landings and take-offs at an actual airport of choice while following, as closely as possible, an ideal flight profile. The film thus obtained is projected for the trainee in the simulator through a servo-controlled anamorphic optical system responding to simulator control movements to distort the images so as to effect an apparent change in the viewpoint of the trainee corresponding to that which would occur in the out-of-the windshield view from a real aircraft in response to the same control movements. Visual systems of this type are commercially available under the trademark VAMP from The Singer Company and are more fully described in a group of U.S. patents typified by U.S. Pat. No. 2,999,322 granted to H. S. Hemstreet.
While the VAMP visual system is far superior in realism and most other respects in comparison to camera-model types, it is restricted in one important aspect insofar as some training applications are concerned. Because the scene to be displayed is recorded on film, no departure from the image content of the film is possible. Thus, for example, if the film depicts the scene through the windshield of an aircraft as it makes its final landing approach, flares, touches down and rolls out along the runway, this is the scene which must inevitably be displayed to the simulator pilot even if he should decide that he had missed his approach and rejects the landing. The VAMP visual system effects apparent perspective displacement by use of anamorphic distortion; while this permits substantial deviations both laterally and in altitude from the scene as recorded on the film, it is nevertheless incapable of a total departure from that scene. Accordingly, it is sometimes referred to as a pre-programmed system.
Pre-programming is not a characteristic of the VAMP visual simulator only but is inherent in any system which utilizes cinematographic film for image generation and, while the limitations it imposes have long been recognized, attempts to overcome them have been only partially successful if at all.
One solution, of course, lies in the resort to image generation not utilizing film. The camera-model system, already described, utilizes a terrain model to avoid the inflexibility of a film-based image generator but at the price of other shortcomings of a more serious nature also described above.
The utilization of digital computer image generator (CIG) visual systems (as shown in U.S. Pat. No. 3,621,214, for example) is a comparatively recent development which avoids the use of film but these are characterized by very high cost due to the need for extremely high speed computation and vast memory capacity. Moreover, at the present time, the display achievable is inferior even to that of a camera-model system in that it has the disadvantages of any system using a CRT display, viz, raster lines, limited brightness, etc., and in addition, in their current stage of development, CIG systems present a display which is somewhat more symbolic than realistic in appearance.
Attempts to introduce greater flexibility into film-based visual systems have proposed the subdivision of the frames of cine film into multiple zones as shown in U.S. Pat. Nos. 3,574,262 and 3,580,978. This necessarily compromises one of the major advantages of film-based systems by effectively reducing the frame size and, therefore, the resolution of the display. (The importance of large frame size in applications of this type is attested by the fact that the commercial VAMP visual system, mentioned above, utilizes 65/70mm film.)
It is, therefore, a principal general object of the invention to improve film-based visual systems by overcoming or at least mitigating the disadvantages described above.
A more specific object is to increase the flexibility of film-based image generation systems without sacrifice of image quality.
Another object is the provision of a novel, film-based simulator visual system having greater latitude in display variability than comparable prior art systems.